I'm actually curious on what grounds TagLib is not included; it's used by a
number of applications for both GNOME and KDE. The only thing that I can
imagine is that this is related to the MP3 components, but TagLib does not
contain an MP3 decoder...

Btw, the current BuildRequires are wrong. Should be "BuildRequires: taglib-devel
libtunepimp-devel".
Only taglib-devel is in Extras already, libtunepimp-devel is not included yet
and wants to compile in the MAD mp3 decoder by default, btw. So a full-featured
libtunepimp is not possible for Extras.